JP4538410B2 - Method for manufacturing translucent substrate with transparent conductive film - Google Patents

Description

  The present invention relates to a highly transparent translucent substrate with a conductive film.

  As a translucent substrate with a thin film transparent conductive film, Japanese Patent Application Laid-Open No. 7-242442 discloses that the thickness of tin-doped indium oxide (ITO) is 23 nm and the transmittance at 550 nm is 95.1% (400 nm from FIG. 1). In Japanese Patent Application Laid-Open No. 7-242443, the ITO film thickness is 20 nm and the transmittance is 400 nm, 86.8%, 500 nm, 92.2%. Are listed. On the other hand, it was thought that the conductive film of a transparent substrate with a transparent conductive film would not be a continuous film if it was an ultrathin film of nm level.

Although a highly transparent translucent substrate with a transparent conductive film is required, even the ITO film described in the above publication is not necessarily highly transparent in the visible light region (380 to 780 nm).
It is an object of the present invention to provide a transparent substrate with a transparent conductive film that is sufficiently highly transparent. As a result of intensive studies to solve the above-mentioned problems, the present inventors have succeeded in obtaining a continuous film of an ultra-thin film of a translucent substrate with a transparent conductive film and completed the present invention. .

That is, the present invention is as follows.
(1) A continuous tin-doped indium oxide thin film having a film thickness of 9 to 2 nm and a maximum surface roughness of 1 to 20 nm on a light-transmitting substrate using a pyrosol method. A method for producing a light-transmitting substrate with a transparent conductive film, comprising forming a transparent conductive film that is an aggregate of crystals.
(2) The method for producing a transparent substrate with a transparent conductive film according to (1), wherein an average surface roughness of the transparent conductive film is in a range of 0.1 to 10 nm.
(3) The transparent conductive film with a transparent conductive film according to (1) or (2), wherein the transparent conductive film has a uniform distribution of tin atoms in a thin film of tin-doped indium oxide. Production method.
(4) The transparent conductive film-attached transparent substrate with a transparent conductive film according to any one of (1) to (3), wherein the transparent conductive film is formed at a temperature of 400 to 750 ° C. Production method.
(5) The translucent substrate with a transparent conductive film according to any one of (1) to (4), wherein the translucent substrate with a transparent conductive film has a transmittance for light having a wavelength of 400 nm of 88% or more. Manufacturing method of optical substrate.
(6) The transparent substrate with a transparent conductive film according to any one of (1) to (5), wherein the transparent substrate with a transparent conductive film has a transmittance of 85% or more for light having a wavelength of 350 nm. Manufacturing method of optical substrate.
(7) The translucent substrate with a transparent conductive film according to any one of (1) to (6), wherein the translucent substrate with a transparent conductive film has a total light transmittance of 90% or more. Manufacturing method.

  In the present invention, as the light-transmitting substrate, a glass substrate or a resin substrate that is easily available and excellent in light transmittance and other physical properties is preferable. Glass substrates can be broadly classified into alkali glass and non-alkali glass. Alkaline glass is inexpensive and easy to obtain, so it has great cost merit, but it contains about 13 to 14% alkali metal oxide, and measures to prevent contamination from these alkali metals are necessary. It has drawbacks such as poor heat resistance. On the other hand, the alkali-free glass is preferable because it does not have to worry about alkali metal contamination and has heat resistance.

Examples of the alkali glass include soda lime glass having a composition of SiO ₂ : 72 wt%, Al ₂ O ₃ : 2 wt%, CaO: 8 wt%, MgO: 4 wt%, and Na ₂ O: 13.5 wt%. As an alkali-free glass, for example, borosilicate (7059) having a composition of SiO ₂ : 49 wt%, Al ₂ O ₃ : 10 wt%, B ₂ O ₃ : 15 wt%, BaO: 25 wt% is used. ) Glass, SiO ₂ : 53 wt%, Al ₂ O ₃ : 11 wt%, B ₂ O ₃ : 11 wt%, CaO: 2 wt%, MgO: 2 wt%, BaO: 15 wt%, ZnO: 6 Borosilicate (AN) glass having a composition of wt%, SiO ₂ : 54 wt%, Al ₂ O ₃ : 14 wt%, B ₂ O ₃ : 15 wt%, MgO: 25 wt% of borosilicate (NA- 40) Glass, broom Acid (BLC) glass, alkali-free (OA-10) glass, and the like are known.

As the surface roughness of the substrate such as glass, average surface roughness Ra ≦ 10 nm and maximum surface roughness Rmax ≦ 50 nm may be preferably polished. In particular, the substrate using alkali glass has an average surface roughness Ra ≦ 10 nm and the maximum surface roughness Rmax ≦ 50 nm, and the substrate using alkali-free glass has an average surface roughness Ra ≦ 5 and a maximum surface roughness Rmax ≦ 20 nm. Is preferred. The lower limit is not particularly restricted, but is usually about average surface roughness Ra ≧ 0.1 nm and maximum surface roughness Rmax ≧ 0.5 nm. As a method for adjusting the surface roughness of the glass substrate within the above range, mirror polishing using diamond, cerium oxide or the like may be performed.
Specific examples of the resin include films, sheets, or plates made of polyester such as polycarbonate, polyethylene terephthalate, and polyarylate, polyethersulfone resin, amorphous polyolefin, polystyrene, acrylic resin, and the like. In particular, from the viewpoint of transparency and moldability, a polyolefin-based transparent thermosetting resin is preferable, and a polyolefin-based polymer obtained by polymerizing a composition containing a polyfunctional monomer having two or more unsaturated groups. A copolymer is more preferably used.

  Specific examples of the polyfunctional monomer having two or more unsaturated groups include (i) ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, glycerol di (Meth) acrylate, glycerol tri (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra ( Di-, tri-, tetra- (meth) acrylates of polyhydric alcohols such as (meth) acrylate, (ii) aromatic polyfunctional monomers such as p-divinylbenzene, o-divinylbenzene, (iii) (meta Acry Esters such as vinyl acetate, (meth) acrylic acid allyl ester, (iv) dienes such as butadiene, hexadiene, pentadiene, (v) phosphazene skeleton with polyfunctional groups introduced from dichlorophosphazene as a raw material Monomer, (vi) polyfunctional monomer having a heteroatom cyclic skeleton such as triallyl isocyanurate, and the like.

  The transparent thermosetting resin preferably contains various ultraviolet absorbers, antioxidants and antistatic agents from the viewpoints of light resistance, oxidation deterioration resistance and antistatic properties. When the transparent thermosetting resin is the above polyolefin copolymer, the polyolefin copolymer is preferably one using a monomer having ultraviolet absorbing property or antioxidant property. Preferred examples of such a monomer include a benzophenone ultraviolet absorber having an unsaturated double bond, a phenylbenzoate ultraviolet absorber having an unsaturated double bond, and a hindered amino group as a substituent (meta ) Acrylic acid monomer. These monomers are preferably used in a range of 0.5 to 20 wt% with respect to the total amount of monomers used to obtain the target polyolefin-based copolymer.

The surface state of the resin substrate to be used is a surface in which the root mean square value of the surface roughness is 30 nm or less and the number of projections of 60 nm or more existing in a 500 μm square region on the flat surface is 20 or less. Is preferred. The “surface roughness square mean value” as used in the present invention for the above flat surface is the mean square value of the deviation from the average value of the height of the surface irregularities, and the size of the surface irregularities. Means degree. Further, “the number of protrusions of 60 nm or more existing in a 500 μm square region on the flat surface” as used in the present invention exists in each of the 500 μm square regions arbitrarily set at ten locations on the flat surface. It means an average value of the number of protrusions having a height of 60 nm or more. The height and number of protrusions in each region can be determined using an electron microscope, an atomic force microscope, or the like.
As long as it has a flat surface as described above, it may be obtained by any polymerization method and molding method. In addition, the thickness can be appropriately selected according to the intended use and the like. However, when the transparent thermosetting resin substrate is made of the above-described polyolefin copolymer, the thickness considers mechanical properties. It is preferable that it is 0.1-1.5 mm, and it is more preferable that it is 0.1-1.0 mm.

An inorganic oxide film can be formed between the light-transmitting substrate and the transparent conductive film as necessary in order to prevent an alkali component or the like from entering the transparent conductive film. Specifically, as the inorganic oxide film, silicon oxide (SiO _x ), aluminum oxide (Al ₂ O _x ), titanium oxide (TiO _x ), zirconium oxide (ZrO _x ), yttrium oxide (Y ₂ O _X), ytterbium oxide _{(Yb 2 O} X), magnesium oxide _(MgO X), tantalum oxide _{(Ta 2 O} X), cerium oxide (CeO _X) or hafnium oxide _(HfO X), the organic polysilane Examples thereof include a polysilane film formed from a compound, an MgF ₂ film, a CaF ₂ film, a film made of a composite oxide of SiO _X and TiO _X , and the like.

The film thickness of the inorganic oxide film can be appropriately changed depending on the material, but is generally in the range of 2 to 20 nm. When the film thickness is too thin, it is impossible to prevent the alkali component or the like from entering. On the other hand, if the film thickness is too thick, the light transmittance is lowered.
The flatness of the surface of the inorganic oxide film is desirably as high as the flatness of the flat surface of the substrate that is the base of the inorganic oxide film. Such flat inorganic oxide films can be formed by sputtering methods such as direct current method, magnetron method, high frequency discharge method, vacuum deposition method, ion plating method, plasma CVD method, dipping method, spray pyrolysis method, pyrosol. It can be formed by a method such as a method. Regardless of which method is used to form the inorganic oxide film, it is preferable that the substrate temperature at the time of film formation is a temperature at which the substrate does not substantially undergo thermal deformation.

Examples of the transparent conductive film include films of tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), aluminum-doped zinc oxide, FTO, ATO, ZnO, SnO ₂ , In ₂ O ₃ , and preferably ITO. It is a membrane. The transparent conductive film is required to be a continuous film that is thin as thin as possible to increase the light transmittance, but does not have an island-like structure. Therefore, the film thickness is 12 to 2 nm, preferably 10 to 2 nm, and the light transmittance is increased. For this purpose, 9 to 2 nm is preferable, and for increasing the light transmittance, 8 to 2 nm is preferable. The light transmittance of the light-transmitting substrate with a transparent conductive film of the present invention is preferably 88% or more, more preferably 90% or more, and the total light transmittance is preferably 90% or more, with respect to light having a wavelength of 400 nm. Preferably it is 92% or more, More preferably, it is 93% or more. In addition, the translucent substrate with a transparent conductive film also preferably has a transmittance of 85% or more for light having a shorter wavelength of 350 nm, which is preferably larger.

When ITO is used as the transparent conductive film, it usually contains In ₂ O ₃ and SnO _{2 in a} stoichiometric composition, but the amount of oxygen may be slightly deviated from this. When InO _X · SnO _Y , X is preferably in the range of 1.0 to 2.0 and Y is in the range of 1.6 to 2.4. The mixing ratio of SnO ₂ to In ₂ O ₃ is preferably 0.05 to 40% by weight, more preferably 1 to 20% by weight, and further preferably 5 to 12% by weight. A high ratio of SnO ₂ increases thermal stability.

The method for producing the transparent conductive film is not particularly limited as long as it is a method for forming a thin film on a substrate. Specifically, a sputtering method, an electron beam method, an ion plating method, a screen printing method, or a chemical vapor method is used. Examples thereof include a phase growth method (CVD method), a spray pyrolysis method, a pyrosol method, and the like. Particularly, a spray pyrolysis method and a pyrosol method can be preferably exemplified.
More specifically, according to the sputtering method, a mixture of a metal (for example, indium, zinc, etc.) and a metal to be doped (for example, tin, fluorine, fluorine compound, aluminum, etc.) and oxygen gas, or a metal oxide (for example, oxidation) According to an electron beam method or an ion plating method, a metal (for example, indium, zinc, etc.) and a metal to be doped (for example, tin, fluorine, fluorine) are used. The transparent conductive film can be formed by using a mixture of a compound, aluminum, or the like) and oxygen gas, or a sintered metal oxide (for example, indium oxide, zinc oxide, etc.) as an evaporating substance. .

When a conductive film made of ITO is formed by sputtering, it is preferably formed by DC sputtering using a target in which SnO ₂ is doped in In ₂ O ₃ or RF sputtering.
The sputtering gas is not particularly limited, and an inert gas such as Ar, He, Ne, Kr, or Xe, or a mixed gas thereof may be used. Further, these gases, the O ₂ may contain 20% or less. The pressure during sputtering of such a sputtering gas is usually about 0.1 to 20 Pa.

The substrate temperature during film formation is preferably in the range of 150 to 500 ° C, particularly 200 to 400 ° C.
Heat treatment can be performed as desired after forming a conductive film such as ITO. The temperature for the heat treatment is preferably in the range of 100 to 550 ° C., more preferably 150 to 300 ° C., and the treatment time is preferably 0.1 to 3 hours, more preferably 0.3 to 1 hour. preferable. The treatment atmosphere is preferably air, nitrogen, oxygen, hydrogenated nitrogen atmosphere, organic solvent-added air or nitrogen atmosphere.

As the indium compound used in the CVD method, spray pyrolysis method, pyrosol method and the like, a substance that is thermally decomposed to become indium oxide is preferable. Specifically, indium trisacetylacetonate (In (CH ₃ COCHCOCH ₃ ) ₃ ) , Indium trisbenzoylmethanate (In (C ₆ H ₅ COCHCOC ₆ H ₅ ) ₃ ), indium trichloride (InCl ₃ ), indium nitrate (In (NO ₃ ) ₃ ), indium triisopropoxide (In (OPr- i) ₃ ) and the like can be exemplified, and indium trisacetylacetonate is preferable.
Further, as the tin compound, those which are thermally decomposed to become stannic oxide can be preferably used. Specifically, stannic chloride, dimethyltin dichloride, dibutyltin dichloride, tetrabutyltin, stannic octoate ( Sn (OCOC ₇ H ₁₅ ) ₂ ), dibutyltin maleate, dibutylzuzuacetate, dibutyltin bisacetylacetonate and the like.

In addition to the indium compound and the tin compound, as a third component, a periodic table group 2 element such as Mg, Ca, Sr and Ba, a group 3 element such as Sc and Y, La, Ce, Nd, Lanthanoids such as Sm and Gd, Group 4 elements such as Ti, Zr and Hf, Group 5 elements such as V, Nb and Ta, Group 6 elements such as Cr, Mo and W, Group 7 elements such as Mn Group elements such as Co, Co, Group 10 elements such as Ni, Pd, and Pt, Group 11 elements such as Cu and Ag, Group 12 elements such as Zn and Cd, and Group 13 elements such as B, Al, and Ga An ITO film can be formed by adding a simple substance such as a group element, a group 14 element such as Si, Ge or Pb, a group 15 element such as P, As or Sb, a group 16 element such as Se or Te, or a compound thereof. It is also preferable to form.
The addition ratio of these elements is preferably about 0.05 to 20 atomic% with respect to indium. The addition ratio varies depending on the addition element, and the element and the addition amount that meet the target resistance value can be selected as appropriate. it can.

As a method for forming an ITO film on a glass substrate by a pyrosol method or a spray pyrolysis method, an indium compound exemplified above as an organic solvent such as alcohols such as methanol and ethanol, and ketones such as acetone, methyl butyl ketone, and acetylacetone And a tin compound is dissolved to form a mixed solution, and then the mixed solution is finely dispersed in a carrier gas and contacted with a glass substrate heated to 400 to 750 ° C., preferably 400 to 550 ° C., under normal pressure. Can be manufactured. The mixed solution can be atomized by an ultrasonic atomization method, a spray method, or the like, and an ultrasonic atomization method capable of stably generating fine particles having a uniform particle diameter is preferable. As the carrier gas, an oxidizing gas, usually air, is used.
When the pyrosol method is used, crystal nuclei having an ITO film composition are formed on the glass substrate by contact between the fine particles of the mixed solution and the heated glass substrate, and contact with adjacent nuclei as the nuclei grow. However, since the contact nuclei are constrained to each other, the growth is mainly in the direction perpendicular to the substrate surface. As a result, an ITO film that is a composite of oriented columnar single crystals can be easily obtained. This ITO film is etched. Good sex. When an ITO film is formed by the pyrosol method, tin atoms are uniformly distributed in the film from the substrate toward the film surface. In this case, polishing is not performed to make the obtained film uniform. May be. In this case, “uniform” means that tin atoms are not segregated on the film surface, and the value of the film surface does not exceed twice the average value in the film in the atomic ratio of tin / indium.

  The transparent conductive film is preferably a crystalline conductive film. The film structure is not particularly limited, and may be a structure in which massive crystals are stacked, but among them, an aggregate of columnar single crystals is preferable. The transparent conductive film preferably has a grain size in the range of 20 to 100 nm. The shape of the crystallite is not particularly limited, but is preferably a spherical shape or a spheroid shape, and preferably has fewer protrusions and corners. In addition, the shape and size of the crystallite can be evaluated by observing the surface using a transmission microscope (TEM). The transparent conductive film of the present invention has a maximum surface roughness Rmax of preferably 1 to 20 nm, more preferably 1 to 15 nm, and an average surface roughness Ra of preferably 0.1 to 10 nm, more preferably 0. .1 to 1 nm.

As described above, the conductive film formed on the substrate may be further irradiated with UV ozone or ions such as oxygen ions, nitrogen ions, and argon ions as necessary. The conditions of UV ozone irradiation are, for example, main wavelengths of 2537 angstroms and 1849 angstroms of the light source, an oxygen gas introduction amount of 10 liters / minute in the irradiation tank, a substrate temperature of 10 to 30 ° C., and an irradiation time of 10 minutes to 5 hours. The ion irradiation conditions are, for example, an irradiation tank internal pressure of 10 ⁻⁶ to 10 ⁻¹ Pa, an irradiation drive voltage of 10 to 1000 V, and an irradiation time of 10 seconds to 1 hour. Moreover, you may perform UV ozone irradiation and ion irradiation which were mentioned above with respect to the electrically conductive film which has a desired surface asperity. When UV ozone irradiation or ion irradiation is performed, the surface of the conductive film can be cleaned without damaging the substrate.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, the scope of the present invention is not limited to an Example.

[ Example 1 (Reference Example)]
An ITO film was formed on the glass substrate by the pyrosol method. That is, a borosilicate (BLC) glass polishing substrate (260 × 220 × 0.4 mm) pre-coated with a SiO ₂ film (film thickness 10 nm) was placed in a conveyor furnace heated to 500 ° C. by a belt conveyor, and the atomic ratio was Making acetylacetone solution of stannic chloride-indium acetylacetonate containing 12% tin atom in the form of mist droplets, blowing air into the conveyor furnace as carrier gas, and contacting the surface of the glass substrate for thermal decomposition. As a result, an ITO film having a thickness of 12 nm was formed. The resulting ITO film had a surface resistance value of 1.7 KΩ / □. When the film surface was observed with an atomic force microscope (AFM), the average surface roughness Ra was 0.7 nm, and the maximum surface roughness Rmax was 12 nm. The transmittance of spectral characteristics of the obtained ITO glass is shown in FIG. 1, and the reflectance is shown in FIG.

[ Example 2 (reference example)]
An ITO film having a film thickness of 10 nm was formed in the same manner as in Example 1 except that the belt conveyor speed and the chemical atomization amount were adjusted.
The analysis results of the obtained ITO glass are shown in Table 1, the transmittance of spectral characteristics is shown in FIG. 1, and the reflectance is shown in FIG.

[ Example 3 ]
An ITO film was formed on the glass substrate by the pyrosol method. That is, a borosilicate (BLC) glass polishing substrate (260 × 220 × 0.4 mm) pre-coated with a SiO ₂ film (film thickness 10 nm) was placed in a conveyor furnace heated to 500 ° C. by a belt conveyor, and the atomic ratio was Making acetylacetone solution of stannic chloride-indium acetylacetonate containing 12% tin atom in the form of mist droplets, blowing air into the conveyor furnace as carrier gas, and contacting the surface of the glass substrate for thermal decomposition. As a result, an ITO film having a thickness of 8 nm was formed. When the film surface was observed by AFM, the average surface roughness Ra was 0.8 nm, and the maximum surface roughness Rmax was 13 nm. The transmittance of spectral characteristics of the obtained ITO glass is shown in FIG. 1, and the reflectance is shown in FIG.

[ Example 4 ]
An ITO film having a film thickness of 6 nm was formed in the same manner as in Example 3 except that the belt conveyor speed and the chemical atomization amount were adjusted.
The analysis results of the obtained ITO glass are shown in Table 1, the transmittance of spectral characteristics is shown in FIG. 1, the reflectance is shown in FIG. 2, and the surface photograph obtained by AFM is shown in FIG.

ITO glass obtained in Examples 1 to 4 ITO film be washed is not also eroded alkali peeling without peeling.

[ Example 5 (reference example)]
A film thickness is obtained in the same manner as in Example 1 except that the chemical agent is an acetylacetone solution of stannic chloride-indium acetylacetonate containing 5% tin atom and the belt conveyor speed and the chemical atomization amount are adjusted. A 10 nm ITO film was formed.
The total light transmittance of the obtained ITO glass was 93%. The composition of the metal atoms in the film was measured using ESCA, tin atoms were present uniformly without segregation in the film from the surface toward the substrate. The measurement results are shown in FIG.

[ Example 6 ]
An ITO film having a film thickness of 8 nm was formed in the same manner as in Example 5 except that the belt conveyor speed and the chemical atomization amount were adjusted. The total light transmittance of the obtained ITO glass was 93%. The composition of the metal atoms in the film was measured using ESCA, tin atoms were present uniformly without segregation in the film from the surface toward the substrate. The measurement results are shown in FIG.

The translucent substrate with a transparent conductive film of the present invention is highly transparent, can save light and save energy, and is suitable as an electrode for a liquid crystal display (LCD), a liquid crystal light control device, an LCD lens, etc. The utility value of is high.

FIG. 1 shows the spectral characteristics (transmittance) of the ITO glass prepared in Examples 1-4. FIG. 2 shows the spectral characteristics (reflectance) of the ITO glass prepared in Examples 1-4. FIG. 3 is a photograph of the surface of the ITO glass prepared in Example 3 obtained with an atomic force microscope. FIG. 4 shows the measurement results of the contents of indium and tin in the depth direction of the ITO film by ESCA of the ITO glass prepared in Examples 5 to 6.

Claims (7)

Aggregation of columnar single crystals on a light-transmitting substrate, which is a continuous tin-doped indium oxide thin film having a thickness of 9 to 2 nm and a maximum surface roughness of 1 to 20 nm using a pyrosol method. A method for producing a transparent substrate with a transparent conductive film, comprising forming a transparent conductive film as a body. The average surface roughness of the said transparent conductive film is the range of 0.1-10 nm, The manufacturing method of the transparent substrate with a transparent conductive film of Claim 1 characterized by the above-mentioned. The method for producing a transparent substrate with a transparent conductive film according to claim 1, wherein the transparent conductive film has tin atoms uniformly distributed in a thin film of tin-doped indium oxide. The method for producing a transparent substrate with a transparent conductive film according to any one of claims 1 to 3, wherein the transparent conductive film is formed at a temperature of 400 to 750 ° C on the substrate. The translucent substrate with a transparent conductive film according to any one of claims 1 to 4, wherein the translucent substrate with a transparent conductive film has a transmittance of 88% or more for light having a wavelength of 400 nm. Manufacturing method. The translucent substrate with a transparent conductive film according to any one of claims 1 to 5, wherein the translucent substrate with a transparent conductive film has a transmittance for light having a wavelength of 350 nm of 85% or more. Manufacturing method. The method for producing a transparent substrate with a transparent conductive film according to claim 1, wherein the transparent substrate with a transparent conductive film has a total light transmittance of 90% or more. .

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